Beta-Theta - http://www.beta-theta.com/ Gives general definitions, background and examples from the science fields of biology, physics, chemistry, math, and history. Includes forum boards.
RefScout - http://www.refscout.com/ A weekly, scientific reference mailing service.
Knovel - http://knovel.com Online reference collection used by applied scientists and practicing engineers to quickly locate technical information.
Physics and Science Reference by PhysLINK.com - http://www.physlink.com/Reference/Index.cfm Includes physical constants, online unit conversions, periodic table of elements, exact time, fundamental physical formulae and equations.
Eformulae.com - http://www.eformulae.com Online resource providing engineering, science, math, physics and chemistry formulae for reference.
CalcTool - http://www.calctool.org/ Directory of simply-presented javascript calculators and equations for making common calculations. Provides quick, simple online calculation and unit conversion tools.
DOE Community - http://www.osti.gov/doecommunity/ Searchable database for reports that are generated by federally funded projects.
Astronomical Constants from NASA - http://www.ksc.nasa.gov/facts/faq04.html Contains astronomical/space constants and equations.
Science and Engineering Encyclopedia - http://www.diracdelta.co.uk Descriptions, equations, calculators, conversions and material data for engineering, mathematics, physics and chemistry.
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